The present invention is directed to linear thrusters and, more particularly, to fluid operated linear thrusters which are significantly stronger yet more compact and simpler in construction than the prior linear thrusters.
A wide variety of fluid operated linear thrusters have been available in the past. These have been employed for example for the positioning of work pieces or tools on production lines. These prior linear thrusters typically are non-rotatable and include a fluid operated piston and cylinder which moves a tooling plate back and forth in a linear reciprocating fashion, and a pair of spaced guide shafts which are supported by linear slide bearings, and which stabilize the thruster against rotation, strengthen it against side forces and moments and guide the tooling plate during operation. Although the prior linear thrusters have performed well in the many applications in which they have been used, their usefulness is somewhat limited by the maximum side loads, moments and deflection to which they may be subjected during use, particularly at their maximum stroke. The maximum loads and moments that can be accommodated by the described prior linear thrusters rapidly decrease in magnitude as the stroke length of the linear thruster increases. Thus, either the loads, moments and/or deflections must be limited for a given sized and stroke linear thruster, and if greater loads, moments or deflections must be accommodated, the size, bulkiness and volumetric space requirements of the prior linear thrusters must also be substantially increased.
It has been proposed to eliminate the spaced guide shafts of the prior linear thrusters and, instead, provide a stationary guide beam and a moveable load beam surrounding the fluid operated piston and cylinder. This load beam permits a substantial increase in the support and guide surfaces making possible substantial reductions in deflection and increases in the resistance to side loads and moments, particularly where the cross-section of the load beam is non-circular and multisided in shape. It is a principal purpose of the present invention to further substantially improve upon such multisided cross-section linear thrusters.
In the linear thrusters incorporating the principles of the present invention, deflection can be substantially decreased and maximum side loads and moments can be substantially increased, while at the same time reducing the complexity and expense of the linear thrusters of the present invention. Moreover, "pinch points" which frequently existed in the typical prior linear thruster constructions, i.e. locations between which human body parts may be caught or pinched as the parts of the thruster move relative to each other, can be essentially eliminated in the linear thrusters incorporating the principles of the present invention. Significantly, the volumetric space requirements of the linear thrusters of the present invention also may be substantially and considerably reduced over the requirements of the prior linear thrusters, thereby permitting substantial miniaturization and increased compactness of systems incorporating the linear thrusters of the present invention. Additionally, the linear thrusters of the invention are receptive to the internal placement of many of the components which were previously mounted externally of the thruster, and all of the fittings for the operating fluid may be positioned at one end of the thruster to further facilitate increased volumetric space efficiency and compactness.
One important feature of the present invention is that the fluid power cylinder for the operation of the linear thruster may be formed as an intimate part of the load beam and move with it, and the piston may be fixed. This permits a substantial reduction in material needed to form the cylinder because the cylinder is directly supported by the load beam. Moreover, the pressurized operating fluid may be readily communicated to and from piston through the piston rod because both are stationary. This greatly reduces the complexity of the thruster and shortens the fluid path to permit reduction in size and weight of the linear thruster and improve its strength.
Another important advantage of the linear thrusters incorporating the principles of the present invention are that a number and variety of different features may be provided which may be located internally of the linear thruster. This streamlines the exterior of the thruster which permits the improved ability to clean the work area, reduction in possible personnel hazards and damage to and by exteriorly located attachments. Such features which may be located internally may for example include stroke adjustment components, position sensing components and the communication of the electrical or fluid energy to the distally located tooling plate or tool mounted thereto.
Still another principal advantage of the present invention is that the exterior of the linear thruster may be formed, for example by extrusion during manufacture, with useful ridges, grooves, and channels which may be capable of accommodating fastening mechanisms for easily fastening the linear thruster itself to a base plate, or to accommodate position sensors.
Still another principal advantage of the present invention is that it is relatively simple and inexpensive to manufacture and accommodates relatively large tolerances without detrimental effect to its operation. Moreover, the linear thruster of the present invention may be simply adapted to clean room use.
In one principal aspect of the present invention, a fluid operated linear thruster comprises a guide beam having an elongate passage therein defined by internal walls in the guide beam, and a load beam positioned in the passage of the guide beam for reciprocation therein. The load beam has an outer wall which is sized and shaped so as to be supported and guided at least at two spaced locations on the internal walls of the guide beam during reciprocation of the load beam in the passage of the guide beam, and at least one of the aforementioned passage of the guide beam and/or outer wall of the load beam is multisided in cross-section. The load beam includes a mounting for mounting a load thereon for movement with the reciprocating load beam. A piston is located in the load beam and the load beam is reciprocally movable relative to the piston. A fluid inlet communicates a source of fluid under pressure to at least one side of the piston to urge the load beam to reciprocally move in the passage and relative to the piston, and between a first position and a second position while being supported and guided by the aforementioned at least two spaced locations.
In another principal aspect of the present invention, both the passage in the guide beam and the outer wall of the load beam are multisided in cross-section, and preferably square in cross-section.
In still another principal aspect of the present invention, the load beam is located substantially within the guide beam when it is in its first position, the guide beam has first and second opposite ends, and the load beam extends from the first end of the guide beam when the load beam is in its aforementioned second position.
In still another principal aspect of the present invention, the fluid inlet includes at least first and second fluid inlets to communicate a source of fluid under pressure to opposite sides of the piston, and both the first and second fluid inlets are positioned on the guide beam adjacent the second end of the guide beam.
In still another principal aspect of the present invention, the piston includes a piston rod which is mounted, preferably stationarily, at the second end of the guide beam.
In still another principal aspect of the present invention, the fluid inlet communicates with the piston rod to communicate fluid under pressure to at least one and preferably both sides of the piston through the piston rod.
In still another principal aspect of the present invention, the piston is stationarily mounted relative to the guide beam and the load beam is reciprocally moveable relative to the piston.
In still another principal aspect of the present invention, the guide beam is extruded to form its multisided cross-section and one or more channels are extruded on the exterior of the guide beam so that the channels may perform a variety of functions including reception of fastenings for mounting the linear thruster to a base and/or attachment of position sensing means for sensing the position of the load beam.
In still another principal aspect of the present invention, the load beam has an elongate axis and a plurality of channels opening to at least one end of the load beam. The channels are spaced from each other, extend longitudinally of and within the load beam and substantially parallel to and radially spaced from the axis. At least one such channel extends the length of the load beam and is constructed and arranged relative to a tooling plate on the end of the load beam to communicate fluid and/or electrical energy to the tooling plate to operate a tool when it is mounted on the tooling plate. An adjustment assembly may also be provided for adjusting the distance between the first and second positions of the load beam and may include elements which cooperate with at least one of the channels in the load beam.
In still another principal aspect of the present invention, one or all of the guide beam internal walls and load beam outer walls is coated with a low friction substance, and preferably a solid polymer.
In still another principal aspect of the present invention, the guide beam internal walls and load beam outer wall are spaced from each other and at least one bearing member is positioned in the space between the walls to support and guide the load beam at spaced locations during the reciprocation of the load beam, and the bearing member is preferably formed of a solid, low friction polymer.
These and other objects, features and advantages of the present invention will be more clearly understood through a consideration of the following detailed description.